The deployment of advanced high bit-rate mobile networks has opened up new opportunities for delivering a host of services in a way that was not possible with earlier second generation wireless networks. Third generation systems such as Universal Mobile Telephone Service (UMTS) or even lower bit-rate systems such as High Speed Circuit Switched Data (HSCSD) and General Packet Radio Service (GPRS) specified for use with the Global System for Mobile Communications (GSM) wireless standard, will enable the delivery of new digital services such as video calls and the playback of multimedia applications that are comprised of audio and video clips.
Although the increased bit-rates of UMTS systems widen the possibilities for providing digital services, many estimates forecast that these systems can reliably deliver data rates between 64 to 384 kbit's to moving mobile terminals. Bit bit rates of up to 2 Mbits can be achieved for stationary environments. These rates provide pretty good performance for delivering high quality digital audio and acceptable quality moving image clips. However, at these transfer rates it will be difficult to handle exceedingly high data Intensive tasks such as delivering high quality full-motion video and transferring very large data files to mobile terminals. Attempts at downloading huge data files will likely lead to inconveniently long downloading times which probably would not be the most economical in terms of cost per megabyte. For this and other reasons, alternative broadband delivery channels have been investigated that could provide a practical solution for high data intensive tasks in terms of lower cost and convenience for the parties involved.
One such delivery channel that has shown promise is Digital Video Broadcasting DVB-T). DVB-T, which is related to DVB-C (cable) and DVB-S (satellite), is the terrestrial variant of the DVB standard and is a wireless point-to-multipoint data delivery mechanism developed for digital TV broadcasting and based on the MPEG-2 transport stream for the transmission of video and synchronized audio. DVB has the capability of efficiently transmitting large amounts of data over a radio channel to a high number of users at a lower cost, when compared to data transmission through mobile telecommunication networks using e.g. UMTS/GPRS. DVB-T data rates have been shown to provide up to 4-20 Mbit/s, where the lower end of the range corresponds to reception within a very high speed (300 km/h) moving receiver. Another advantage of DVBT is that it has proven to be exceptionally robust in that it works well in geographic conditions that would normally affect other types of transmissions, such as the rapid changes of reception conditions, and hilly and mountainous terrain.
Digital broadband data broadcast networks are known. As mentioned, an example of such a network enjoying popularity in Europe and elsewhere world-wide is Digital Video Broadcast (DVB) which in addition to the delivery of televisual content is capable of delivering data. Other examples of broadband data broadcast networks that provided under the Advanced Television Systems Committee (ATSC). Both ATSC and DVB utilize a containerization technique in which content for transmission is placed into MPEG-2 packets which act as data containers. Thus, the containers can be utilized to transport any suitably digitized data including, but not limited to High Definition TV, multiple channel Standard definition TV (PAUNTSC or SECAM) and, of course, broadband multimedia data and interactive services.
The combined use of mobile telecommunications with a broadband delivery channel such as DVBT has been proposed in the past in order to achieve efficient delivery of digital services to users on the move. This would take advantage of existing infrastructures in the effort to provide personal communications (already prevalent) and the growing demand for Internet access, together with the expected rise of digital broadcasting, so that users can receive these services with a single device. Furthermore, DVB-T is a cross platform standard that is shared by many countries thereby making frequency compatibility and roaming less of an issue. The combination of the mobile telecom and at a relatively very low cost digital broadband channel provides the possibility of interactive services such as unidirectional and bidirectional services such as audio and video streaming (TV & Radio), file downloads and advanced gaming applications etc.
However, there are some challenges with developing the mobile terminals needed for combined use with e.g. DVB-T. A significant issue to consider is that power consumption for mobile terminals must be low enough to provide sufficient use while operating independently from power sources. DVB-T terminals have In the past had high power consumption rates which make them unsuitable for sustained use. This is partly due to the way DVB operates where receivers regularly access broadcast Service Information (DVB-SI) that accompany DVB signals which assist the receiver/decoder and the viewer to navigate through the array of services offered. The data is also necessary for the receiver/decoder to automatically configure itself to decode the received broadcast stream that is included in the Program Specific Information (PSI) specified by, for example, the MPEG-2 systems standard. The DVB-SI specifies additional data based on data tables that complement the PSI by providing data to aid in the automatic tuning of receiver/decoders and provides additional information intended for display to the user.
In the development of DVB-T, it was envisioned that signal reception would be mainly carried out by set-top boxes in generally stationary environments where power consumption issues were largely unimportant. However with reception by e.g. mobile handheld devices, the requirement of DVB-T to regularly access Service Information data tables places a heavy power burden on the terminal. This is especially the case when the SI tables are accessed even when the user does not want to view a program for some length of time. In mobile terminals that also operate as telecom devices, power consumption is a particularly important issue since users expect sufficiently reasonable battery life for necessary communication purposes which they expect to be available. At present, it is only possible to build DVB-T mobile receivers with only a few hours of operating time. With improved operating life, data packet based terminals can be left on practically all of the time fulfilling the promise of anytime and anywhere mobile communications.
In view of the foregoing, it is desirable to improve the operating times of mobile terminals that are operable with mobile telecommunication and digital broadcast networks.